Do you think we are born with sexual orientation

You are right when you say we don’t choose sexual orientation. Big mistake people that think it  is an option, it isn’t.  But whether you are born with homosexual or heterosexual orientation, or psychological and environmental factors from your early childhood have a bigger role, nobody really knows. There are some points to be considered: it wasn’t prove yet a genetic trace for homosexuality and also there’s not one single event from early childhood that will define 100% if you are going to be homo of heterosexual. The most important thing is that you accept yourself as you are. Keep in mind that heterosexual don’t ask themselves whether they were born like this or whether is a developmental issue. You should do the same. 

That's a very good question.

There's also been discussion that everyone is born as inherently bisexual which may cause the fluctuation of one's sexuality.

No-one knows for sure if one's sexuality is determined at birth or simply a gene that they're born with that may later populate itself.  Also, it's unclear if one's life circumstances actually could actually be the factor that determines their sexuality.

If cancer, diabetes, mental illness, addiction, and other traits can be determined by genetics and hereditary, they, in theory, are based on genes.  The genes I describe don't always show up in one's life immediately at birth.  

 

I am a 70 year old man who has mostly been gay throughout my life though I have also found very many women attractive. I have many gay friends, many of whom think they were born gay.
The only thing I have managed to work out about my own sexuality is that it is somewhat fluid changing from year to year almost.
If there is a 'gay' gene or more likely more than one, then it has less of an effect in some individuals than in others. If there were a simple switch (as with eye colour) then there would be far fewer bisexual people that there are.
I feel that what we do in our lives can change us, regardless of what's coded into our genes. Some fat people can become thin and some thin people become fat yet there are those who cannot change their bodies in this way.
We cannot change our sexual orientation like a hair style but it certainly can change in ways difficult to understand